nimble/ll: Cleanup aux scheduling function
nimble/ll: Cleanup aux scheduling function

Cleanup variable names and comments to make it logical, i.e. there's no
"earliest start" here since we either can schedule aux scan at specific
point of time or not - we can't adjust it.

X-Original-Commit: 09af9bdcf80e0d493180a1e3045402cfb48f55aa

apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble,apache/mynewt-nimble